Long-term stability of liposomes containing both tissue-type plasminogen activator and glu-plasminogen
article
In this study a procedure is described for preparation and storage of liposomes containing glu-plasminogen (Plg) - as a homing device - coupled to the outside of the liposome bilayer and physically entrapped tissue-type Plasminogen Activator (t-PA). Since in this concept both enzyme and substrate are introduced into one formulation, establishing preparation and storage conditions which prohibit plasmin-formation, loss of enzymatic activity and t-PA-leakage for these complex liposomes are of utmost importance. During preparation of these liposomes no interaction between Pig and t-PA was observed under the conditions used(up to 2 h). Plg-activation occurred only in the presence of fibrin fragments. Therefore, no special stability precautions had to be taken during the preparation process. Suitable preparation and freeze-drying conditions were examined for t-PA-liposomes first and subsequently applied to Plg-liposomes and Plg- t-PA- liposomes. Freeze-drying of the liposomes in a Hepes buffer pH 7.5, containing 7.5% (w/v) lactose, resulted in maximal recovery of enzyme activity of both Pig and t-PA. Plg was also shown to retain its fibrin binding capacity upon freeze-drying. Furthermore, no loss of t-PA retention was induced by the freeze-drying procedure under the conditions used, provided that freeze-dried liposomes were not exposed to an extra ultracentrifugation step compared to the non-freeze-dried control liposomes. In conclusion, the described preparation and freeze-drying procedure is considered appropriate.
Chemicals/CAS: alteplase, 105857-23-6; plasminogen, 9001-91-6; tissue plasminogen activator, 105913-11-9
Chemicals/CAS: alteplase, 105857-23-6; plasminogen, 9001-91-6; tissue plasminogen activator, 105913-11-9
TNO Identifier
233257
ISSN
03785173
Source
International Journal of Pharmaceutics, 129(1-2), pp. 191-202.
Pages
191-202
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